Production of 2-methyl-3-buten-2-ol

ABSTRACT

Production of 2-methyl-3-buten-2-ol in which an aqueous acid is allowed to act on 3-methyl-3-buten-1-ol at temperatures of from 20* to 250*C while removing by distillation the 2-methyl-3-buten2-ol formed. 2-methyl-3-buten-2-ol is an important intermediate for the production of terpenes.

United States Patent Mueller et al.

[541 PRODUCTION OF 2-METHYL-3- BUTEN-Z-OL [72] Inventors: HerbertMueller, 53 Carostrasse,

6710 Frankenthal; Dietrich Mangold, 49 l-lermann-Walker-Strasse, 6903Neckargemuend, both of Germany [22] Filed: May 13, 1970 [21] Appl. No.:37,061

[30 Foreign Application Priority Data May 17, 1969 Germany 1925 197.9

52 US. Cl ..260/642, 260/682 [51] Int. Cl. ..C07c 29/00, C07c 1/24 [58]Field of Search ..260/642 [56] References Cited UNITED STATES PATENTS3,344,191 9/1967 Chappell et al ..260/642 2,373,956 4/ 1945 Heame et al...260/642 2,435,078 l/ 1948 Heame et al. ..260/642 [451 Oct. 3, 1972UI'HER PUBLICATIONS Nazarov et al., Chem. Abstracts" Vol. 42, (1948),pages 7730 to 7739, QDlASl.

Nazarov et al., Akad Nask 555R Seris Khim, (1946) pages 4-19-26, LibraryCongress No. AS262. A 62425. 7

Primary Examiner-Leon Zitver Assistant Examiner-Joseph E. EvansAttorney-Johnston, .Root, O'Keeffe, Keil, Thompson A and Shurtleff [57]ABSTRACT 6 Claims, No Drawings PRODUCTION OF 2-METHYL-3-BUTEN-2-OL Thepresent invention relates to a process for the production of2-methyl-3-buten-2-ol by isomerization of 3-methyl-3-buten-l-ol. I

It is known that 2-methyl-3-buten-2-ol can be prepared by reaction ofacetone with acetylene followed by partial hydrogenation of theresultant 2- methyl-3-buten-1-ol (cf. for example Liebigs Annalen derChemie, 596, 37( 1955). The process is very expensive however because inthe first stage special precautionary measures are necessary becauseacetylene is being used and in the second stage the partialhydrogenation using poisoned catalysts requires very exact maintenanceof the reaction conditions. The production of 2-methyl-3-buten-2-ol byadding isopropanol radicals to acetylone at superatmospheric pressure isfurthermore described in French Pat. No. 1,301,882. This process howevergives only unsatisfactory yields.

The object of the invention is a process for the production of2-methyl-3-buten-2-ol according to which 2-methyl-3-buten-2-ol isobtained by a simpler method and in better yields than in.the prior artmethods. a

In accordance with this invention thisand other objects and advantagesare obtained'in a process for the production of 2-methyl-3-buten-2-ol inwhich 3- methyl-3-buten-l-ol is contacted with an aqueous acid at atemperature of from 20 to 250C while removing by distillation the2-methyl-3-buten-2-ol formed.

According to this process, 2-methyl-3-buten-2-ol is obtained in onestage in good yields/The starting material (3-methyl-3-buten-l-ol) canbe prepared in a simple manner by the method of German Printedapplication No. 1,275,049 by reaction of isobutylene with formaldehyde.

The reaction may be carried out in he presence of a monobasic orpolybasic, preferably up to dibasic, organic or inorganic acid. Theaqueous acid generally has a dissociation constant of at least 1 X l'Naturally compounds which are converted in aqueous medium into acidssuch as aluminum chloride may also be used. Examples of suitable acidsare hydrogen chloride, hydrogen bromide, hydrogen iodide, hydrogenfluoride, sulfuric acid, phosphoric acid, p-toluenesulfonic acid,trichloroacetic acid, dichloroacetic acid, chloroacetic acid, formicacid, oxalic acid, and ion exchange resins which contain sulfonic acidgroups or carboxyl groups. The concentration of the aqueous acid isgenerally from 0.01 to 35 percent by weight. Very strong acids, i.e.,acids having a dissociation constant of more than about areadvantageously used in a concentration of 0.01 to 10 percent by weight,particularly from 0.05 to 2 percent by weight. Acids having adissociation constant of less than about 10 are preferably used inamounts of from 0.5 to 25 percent by weight, particularly 1 to 10percent, by weight. It is generally advantageous to use lowerconcentrations of acid when using higher temperatures and to use higheracid concentrations at lower temperatures. Thus it may for example beadvantageous to decrease the acid concentration by about the factor 0.2to 0.1 upon an increase in temperature of for example 30C. Particularlyfavorable results are obtained when using benzene sul- The reaction iscarried out at a temperature of from to 250C, preferably at from 50 to200C. Atmospheric pressure is generally used. It is also possiblehowever to use superatmospheric pressure, for example 5 atmospheres, orsubatmospheric pressure, for example 100 mm Hg.

The ratio by weight of starting material to aqueous acid is generallyfrom 1:5 to 5:1, preferably from 1:2 to 3: 1. It may be advantageousadditionally to use inert organic solvents in the isomerization.Examples of suitable solvents are aromatic or aliphatic hydrocarbonswhich may be nitrated or halogenated such as benzene,

toluene, ethylbenzene, chlorobenzene, cyclohexane,

fonic acids, trichloroacetic acid and particularly oxalic acid or maleicacid.

ligroin, and trichloroethane. The inert solvents are advantageously usedin amounts of 10 to 200 percent by weight, preferably 30 to. percent byweight, with reference to the mixture of starting material and aqueousacid. When using an inert solvent it is advantageous to provide forvigorous mixing of the reaction mixture.

The isomerization may be carried out-continuously or batchwise.Batchwise operation may be carried out for example by heating a mixtureof starting material and aqueous acid in the specified amounts in areactor having a superimposed packed column at atmospheric pressure atthe reaction temperature, the 2-methyl-3- buten-2-ol formed being takenoverhead. Water generally is distilled off from the reaction mixturetogether with the end product. Water is advantageously added to thereaction mixture at the rate at which it is distilled off. It ispreferred to carry out the reaction continuously.

2-methyl-3-buten-2-ol is a valuable intermediate for example for theproduction of terpenes.

The following Examples illustrate the invention. The parts specified inthe Examples are parts by weight.

EXAMPLE 1 Six hundred and seventy parts of 3fmethyl-3-butenl-ol, 535parts of water and 1.67 parts of concentrated sulfuric acid are heatedat boiling temperature for 10 hours in a 2-liter stirred flask having asuperposed column having a height of 1 meter which is packed with glassRaschig rings and provided with a distilling head. During this period,at a distillation temperature of 94 to 95C, water (which is continuouslyreturned to the still) and 660 parts of an organic distillate are takenoff; the latter has the following composition according to gaschromatographic analysis: 6 percent isoprene, 31.8 percent2-methyl-3-buten-2-ol and 57.6 percent 3- methyl-3-buten-1-ol. At aconversion of 43 percent, the yield of 2-methyl-3-buten-2-ol is 72percent of the theory.

EXAMPLE 2 One thousand parts of 3-methyl-3-buten-l-ol, 400 parts ofwater and 2.5 parts of concentrated phosphoric EXAMPLE 3 Fifteen hundredparts of 3-methyl-3-buten-1-ol, 300 parts of water, 2.5 parts ofconcentrated sulfuric acid and 500 parts of ethylbenzene are heated atboiling temperature for 20 hours with vigorous stirring in the apparatusdescribed in Example 1 and by an analogous method to that described inExample 1. The 999 parts of distillate obtained contains the followingsubstances according to gas chromatographic analysis: 7.2 percentisoprene, 14.4 percent 2-methyl-3-buten-2-ol and 27 percent3-methyl-3-buten-lol. Ata conversion of 46 percent, the yield of2-methyl-3-buten-2-ol is 63 percent of the theory.

EXAMPLE 4 One thousand parts of 3-methyl-3-buten-l-ol, 400 parts ofwater and 80 parts of oxalic acid are kept at boiling temperature for 18hours in a manner analogous to that described in Example 1. During thesaid period, 912 parts of an organic distillate is obtained whichaccording to gas chromatographic analysis has the following composition:10.5 percent isoprene, 65 percent 2-methyl-3-buten-2-ol and 23 percent3-methyl-3-buten-l-ol. At a conversion of 79 percent, the yield of2-methyl-3-buten-2-ol is 75 percent of the theory.

By proceeding as described in Example 4 and using 90 parts of maleicacid instead of the oxalic acid, the conversion is 68 percent and theyield of 2-methyl-3- buten-l-ol is 82 percent.

EXAMPLE The evaporator (having a capacity of about 1000 parts by volume)of a distillation column having about ten theoretical trays is fed eachhour as follows:-

3-methyl-3-buten-lol 45.5 parts water 54.5 parts oxalic acid. 4.5 partsThe feed temperature is 100C. A mixture of water and pentenols boilingat 92C is taken overhead. While the aqueous phase is returned to theevaporator of the column, the organic phase is supplied in the middle ofa second column having eight theoretical trays. 0.8 part of isoprene(boiling point 34C) is taken off at the top of this column. The bottomsof the column is introduced into the lower third of a third columnhaving about 15 theoretical trays. The overhead product obtained here isa 2-methyl-3-buten-2-ol/water azeotrope having a boiling point of 86C.The bottoms of this column are returned to column 1. The product leavingthe evaporator of column 1 and consisting of water, oxalic acid andsmall amounts of 3-methyl-3-buten-1-ol is returned to the reaction afterappropriate con-centration. Whereas 25.7 parts of 2-methyl-3-buten-2-olis obtained in the overhead product of the third column, 15.9 parts of3-methyl-3-buten-1-ol is discharged in the bottoms of the first column(gas chromatographic analysis). At a conversion of 65 percent, there isa yield of 2-methyl-3-buten-2-ol of 87 percent of the theory.

EXAMPLE 6 The procedure of Example 5 is followed but a pressure of 2atmospheres gauge is used in the first column and a 0.5 percent byweiglrilt aqueous oxalic acid is used. The top temperature of e firstcolumn is 127 C. The

mixture of isoprene, water and the pentenols obtained from this columnis separated by distillation in two successive columns at atmosphericpressure as described in Example 5. At a conversion of 69 percent,2-methyl 3-buten-2-ol is obtained in an percent yield.

We claim:

1. A process for the production of 2-methyl-3-buten- 2-ol wherein3-methyl-3-buten-l-ol is 35to a temperature of from 50 to 250 C in thepresence of an aqueous acid having a concentration of 0.01 to 35% byweight and a dissociation constant of at least 1 X 10' the ratio byweight of starting materials to aqueous acid being from 1:5 to 5:1 whileremoving by distillation the 2-methyl-3-buten-2-ol formed.

2. A process as claimed in claim 1 wherein aqueous oxalic acid is used.

3. A process as claimed in claim 1 wherein aqueous maleic acid is used.

4. A process as in claim 1 wherein the 3-methyl-3- buten-l-ol is heatedin the presence of 0.01 to 10 percent by weight of an aqueous acidhaving a dissociation constant of more than about 10''.

5. A process as in claim 1 wherein the 3-methyl-3- buten-l-ol is heatedin the presence of 0.5 to 25 percent weight of an aqueous acid having adissociation constant of less than about 10''.

6. A process as in claim 5 wherein from 1 to 10 percent by weight ofsaid acid is present.

mg? UNITED STATES PATENT oFFieE CETIFICATE OF C0 Patent No. 5,696,155Dated October 5, 1972 lnver'ltms) Herbert Mueller, Dietrich Marigold Itis certified that error appears in the above-identified patent and thatsaid Letters Patent are hereby corrected asshown below:

r- Cover Page, left hand column, insert A'SSIGNEE: Badische Anilin 8c-Soda- Fabrik Aktiengesellschaft, Ludwigshafen am Rhein, Germany Column4, line 27 "55" should read heated Specification-Amendment A Claim 1 1Signed and sealed this 3rd day of April 1973 (SEAL) Attest:

EDWARD M.FLETCHER,JR. I ROBERE'K GOTTSCHALK Attest'ing OfficerCommissioner of Patents

2. A process as claimed in claim 1 wherein aqueous oxalic acid is used.3. A process as claimed in claim 1 wherein aqueous maleic acid is used.4. A process as in claim 1 wherein the 3-methyl-3-buten-1-ol is heatedin the presence of 0.01 to 10 percent by weight of an aqueous acidhaving a dissociation constant of more than about 10
 1. 5. A process asin claim 1 wherein the 3-methyl-3-buten-1-ol is heated in the presenceof 0.5 to 25 percent weight of an aqueous acid having a dissociationconstant of less than about 10
 1. 6. A process as in claim 5 whereinfrom 1 to 10 percent by weight of said acid is present.